Method for paging information in cellular system

ABSTRACT

Provided is a method for transmitting paging information in a cellular system. An object of the method is transmitting paging information which can improve applicability of a limited radio resource by variably and flexibly setting up and mapping a transport channel and a physical channel in order to transmit information notifying start of downlink information from a base station to a terminal in a cellular system for packet transmission. The method includes the steps of: forming a paging channel (PCH) in a transport channel corresponding to generation of paging information; setting a paging indication channel (PICH) based on the paging information and forming the paging indication channel in a radio resource of a physical layer; and allocating the paging channel to the radio resource of the physical layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 12/298,227, filed Oct. 23, 2008 (now pending), thedisclosure of which is herein incorporated by reference in its entirety.The U.S. patent application Ser. No. 12/298,227 is a national entry ofInternational Application No. PCT/KR2007/001997, filed on Apr. 24, 2007,which claims priority to Korean Application Nos. 10-2006-0037522 and10-2007-0038849 filed on Apr. 26, 2006 and Apr. 20, 2007, respectively,the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method for transmitting paginginformation in a cellular system; and, more particularly, to a methodfor transmitting paging information notifying generation of downlinkinformation from a base station to a terminal in a cellular system forproviding a packet service.

BACKGROUND ART

A conventional cellular system is operated by fixedly allocating atransport channel and a physical channel for paging information. Inparticular, in a 3 rd Generation Partnership Project (3GPP) system of aWideband Code Division Multiple Access (WCDMA) method, a paging channel(PCH) is a transport channel and is transmitted through a secondarycommon control physical channel (S-CCPCH), which is a physical layerchannel for transmitting common control information. A forward accesschannel (FACH), which is a transport channel having a similar attributeto the paging channel, and a paging channel can be mapped to theS-CCPCH.

In a conventional WCDMA system, a radio resource is assigned byallocating a code index of orthogonal variable spreading factor (OVSF)with orthogonality. Therefore, an individual OVSF code index isallocated to the S-CCPCH and another physical layer channel may not useor share the OVSF code index allocated to the S-CCPCH. Although there isno information to be transmitted from a base station to a terminalthrough the transport channel PCH and FACH at a given time, the physicallayer channel S-CCPCH exists. Although there is no transmittedinformation in the S-CCPCH, the OVSF code index and another radioresource, i.e., power, are allocated and thus radio resources arewasted.

A general paging procedure is as follows. Terminals are included in aspecific paging group defined for an efficient paging procedure in asystem. Therefore, the base station notifies that a paging messagearrives at terminals included in a corresponding group through thepaging indication channel (PICH), which is a physical layer channel. Theterminals monitor the paging indication channel every monitoring cycle.As a result of monitoring, when it is sensed that indication informationcorresponding to the group including the terminal exists in the pagingindication channel, the terminals search PCH information transmitted tothe S-CCPCH channel and decode paging information that an identifier(ID) such as international mobile subscriber identity (IMSI), temporarymobile subscriber identity (TMSI), UMTS terrestrial radio accessnetwork-radio network temporary identifier (U-RNTI) exists. Theterminals decoding the paging information performs following procedurescorresponding to the paging information.

Also, a plurality of S-CCPCHs may be operated to obtain a pagingcapability according to an environment of the base station and thecapacity for subscribers of the base station. When the base station isinstalled based on a cell specific parameter, the S-CCPCH is staticallyoperated. The radio resource allocating method, which is staticallyoperated in consideration of the maximum capacity, has a merit that acircuit based-system is statically operated, but has a problem that thelimited radio resource is wasted.

A long term evolution (LTE) system standardized in 3GPP to providediverse packet services is a packet based-system. An object of the LTEsystem is to provide a pure packet service. Therefore, in the LTE systemfor providing a packet service having a burst characteristic, efficientand variable methods for utilizing radio resources are needed.Accordingly, a research for simplifying and integrating diverse kinds oftransport channels operated in the conventional WCDMA method are beingprogressed.

DISCLOSURE Technical Problem

An embodiment of the present invention is directed to providing a methodfor transmitting paging information which can improve applicability of alimited radio resource by variably and flexibly setting up and mapping atransport channel and a physical channel in order to transmitinformation notifying start of downlink information from a base stationto a terminal in a cellular system for packet transmission.

Other objects and advantages of the present invention can be understoodby the following description, and become apparent with reference to theembodiments of the present invention. Also, it is obvious to thoseskilled in the art of the present invention that the objects andadvantages of the present invention can be realized by the means asclaimed and combinations thereof.

Technical Solution

In accordance with an aspect of the present invention, there is provideda method for transmitting paging information in a cellular system,including the steps of: forming a paging channel (PCH) in a transportchannel corresponding to generation of paging information; setting apaging indication channel (PICH) based on the paging information andforming the paging indication channel in a radio resource of a physicallayer; and allocating the paging channel to the radio resource of thephysical layer.

In accordance with another aspect of the present invention, there isprovided a method for transmitting paging information in a cellularsystem, including the steps of: creating a paging channel including apaging message (P-MSG) correspondingly to generation of paginginformation; allocating the paging message to a radio resource of aphysical channel; creating scheduling information corresponding to thepaging message; and allocating the scheduling information to a physicallayer control channel.

Advantageous Effects

The present invention can improve applicability of a limited radioresource by variably and flexibly setting up and mapping a transportchannel and physical channel in a method for transmitting informationnotifying start of downlink information from a base station to aterminal in a cellular system for packet transmission.

Also, the present invention can maximally apply a limited radio resourceby variably operating a procedure of notifying generation of downlinkinformation to initiate or restart downlink information transmissionfrom the base station to the terminal in a packet based-cellular system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart describing a paging information transmittingprocedure in accordance with a first embodiment of the presentinvention.

FIG. 2 shows a transport channel and a physical channel in accordancewith the first embodiment of the present invention.

FIG. 3 is a flowchart describing a paging information transmittingprocedure in accordance with a second embodiment of the presentinvention.

FIG. 4 shows the transport channel and the physical channel inaccordance with the second embodiment of the present invention.

FIG. 5 shows a group identifier (ID) to which a part of a terminalscheduling ID is allocated in accordance with an embodiment of thepresent invention.

FIG. 6 shows a physical layer control channel to which scheduling IDinformation is allocated and a radio resource to which paginginformation is variably allocated in accordance with the secondembodiment of the present invention.

FIG. 7 shows an example that the radio resource of the physical layer isvariably allocated and operated corresponding to generation of thepaging information in accordance with an embodiment of the presentinvention.

BEST MODE FOR THE INVENTION

The advantages, features and aspects of the invention will becomeapparent from the following description of the embodiments withreference to the accompanying drawings, which is set forth hereinafter.Therefore, those skilled in the field of this art of the presentinvention can embody the technological concept and scope of theinvention easily. In addition, if it is considered that detaileddescription on a related art may obscure the points of the presentinvention, the detailed description will not be provided herein. Atechnology outline of a cellular system for providing a packet serviceto which the present invention is applied is will be described in brief,and the preferred embodiments of the present invention will be describedin detail hereinafter with reference to the attached drawings.

The cellular system for the packet service may maximize applicability ofa limited radio resource by sharing the radio resource between a basestation and a terminal in consideration of a bust characteristic ofpacket service data differently from a circuit. A 3rd GenerationPartnership Project (3GPP) long term evolution (LTE) system, which isbeing standardized as the cellular system for the packet service shouldsupport bandwidth scalability of a bandwidth ranging 1.25 MHz to 20 MHz.In designing of a general system, scalability for 5 MHz, 10 MHz, and 20MHz bandwidths is assumed.

Conventional paging information is transmitted to the terminals in anidle state, i.e., the terminals performing low power consumption,through a paging channel, and the terminals providing a service througha dedicated channel. In the LTE system, the terminals are defined asfollowing states in consideration of Radio Resource Control (RRC) andMedium Access Control (MAC).

In consideration of RRC, the terminal state is managed as RRC_Connectedand RRC_Idle states. The RRC_Connected denotes a state that the RRC isconnected between the base station and the terminal. In theRRC_Connected state, the base station manages mobility of the terminal,and stores and manages a RRC context. The RRC_Idle denotes a state thatthe RRC is not connected between the base station and the terminal. Inthe RRC_Idle state, access GateWay (aGW) manages mobility of theterminal. The terminal in the RRC_Idle state performs a low powerconsumption, i.e., power saving operation, according to a discontinuousreception (DRX) cycle based on RRC configuration.

In the RRC_Connected state, an MAC mode is divided into a MAC_Activemode and an MAC_Dormant mode and is controlled for a low powerconsumption of the terminal according to activity factors occupying theradio resource between the terminal and the base station. The MAC_Activemode means that uplink synchronization of the physical layer ismaintained and packet information is transmitted/received between thebase station and the terminal. The MAC_Dormant mode means that a bufferis empty without transmitting/receiving packet information between thebase station and the terminal in the MAC_Active. When a packet is nottransmitted/received for a predefined time in the MAC_Active mode, theterminal transfers to the MAC_Dormant mode. In the MAC_Dormant mode, alow power consumption operation is performed according to discontinuousreception (DRX)/discontinuous transmission (DTX) cycle by a scheduler.Also, it may not to maintain the uplink synchronization of the physicallayer by control of the base station.

When it is considered that paging notifying generation of information tobe transmitted on the downlink should be performed on the terminalsperforming the low power consumption according to the DRX/DTX cycle,paging of the LTE system is applied to the terminals in the RRC_Idlestate and the MAC_Dormant mode. In the present invention, paging isperformed on the terminals in the RRC_Idle state, and a method using apaging indication channel, which is a physical layer channel, and amethod to be applied without the paging indication channel, areprovided.

In the packet transmission system, since the terminals in the basestation share radio resources, scheduling information for addressing theradio resource allocated to a terminal or a terminal group should betransmitted such that the terminals in the base station can recognizethe scheduling information. Accordingly, the present invention providesa method for transmitting scheduling information through a physicallayer control channel.

FIG. 1 is a flowchart describing a paging information transmittingprocedure in accordance with a first embodiment of the present inventionand FIG. 2 shows a transport channel and a physical channel inaccordance with the first embodiment of the present invention.

In the present embodiment, paging information is transmitted to theterminals in the RRC_Idle state through the paging indication channel,which is a physical channel. A paging information transmitting procedurewill be described in detail according to the embodiment with referenceto FIGS. 1 and 2 .

When paging information 1 on a terminal or a group of terminals at apredetermined time is generated at step S110, the base station has apaging channel (PCH) included in the transport channel based on thegenerated paging information at step S120.

The scheduler performs scheduling on broadcasting channel (BCH)information, created paging channel information and, traffic informationto be transmitted to the terminal based on a transmission time interval(TTI) at step S130.

In consideration of a DRX cycle for a low power consumption of theterminals in the RRC_Idle state, the base station sets up a pagingindication channel 6 corresponding to the terminal or the terminal groupindicated by the paging information and forms the paging indicationchannel 6 at step S140 such that the terminal in the system can bedivided into groups.

The base station performs mapping on the paging channel with a radioresource block location 9 of a physical layer allocated at TTI 8 as afixed size and location, e.g., a time index and a sub-carrier index,based on a T_(paging indication channel-PCH) value 7 at step S150,modulates and codes a radio resource based on the pre-set up modulatingand coding methods, and transmits the radio resource to the terminal atstep S160. The T_(paging indication channel-PCH) value is a parameternotifying a time difference between the paging indication channel andthe TTI that the paging channel is transmitted. TheT_(paging indication channel-PCH) value is set up as a multiple TTI.

In the present embodiment, a method for dividing a location of thephysical layer radio resource block for paging channel transmission intopaging indication channel groups, and fixing and allocating the locationof the physical layer radio resource block according to each group isadopted. When no paging information is generated (see 2 of FIG. 2 ), thepaging channel does not exist in the transport channel of the radioframe (see 5 of FIG. 2 ). In this case, the paging indication channel isnot also set up. Therefore, downlink shared channel (DL-SCH) informationfor user data transmission and not paging information of the pagingchannel is transmitted to the radio resource block location of thephysical layer fixed and allocated for the paging channel.

FIG. 3 is a flowchart describing a paging information transmittingprocedure in accordance with a second embodiment of the presentinvention and FIG. 4 shows the transport channel and the physicalchannel in accordance with the second embodiment of the presentinvention. A paging information transmitting procedure will be describedin detail with reference to FIGS. 3 and 4 .

When paging information 1 for a terminal or a terminal group isgenerated at a given time at step S310, the base station creates apaging channel 10 including a paging message (P-MSG) based on thegenerated paging information at step S320.

A scheduler performs scheduling on broadcasting channel (BCH)information formed based on a radio frame unit, paging messageinformation and traffic information to be transmitted to the terminalson the basis of TTI at step S330.

The paging message is variably allocated to a radio resource 12 of thephysical channel at step S340.

Scheduling information is created at step S350, allocated to thephysical layer control channel at step S360, and modulated and codedaccording to the pre-determined modulating and coding methods, andtransmitted to the terminal at step S370.

The scheduling information is the minimum information for addressing theallocated radio resource and includes a terminal scheduling identifier(ID), radio resource allocation information indicating a location of theallocated radio resource block, modulation method information and codingmethod information. The scheduling information may further includeadditional information for operation such as retransmission and multipleantenna application.

The terminal scheduling ID is an ID for identifying a specific terminalor a terminal group between the terminal and the scheduler of the basestation. As shown in FIG. 5 , the present invention is operated byreserving and allocating a part of the information included in theterminal scheduling ID as a group ID for paging information. The groupID is an ID used by reserving and allocating a part of a scheduling ID(i.e., a cell radio network temporary identifier (C-RNTI)) for uniquelyidentifying a terminal. A base station may operate by reserving at leastone scheduling ID.

Meanwhile, the group ID may be used to indicate downlink informationtransmission below.

The radio resource allocation contents inform a radio resource locationor section of an Orthogonal Frequency Division Multiplexing (OFDM)method, which is divided into a frequency region and a time region. Themodulation method contents inform which modulation method among aplurality of modulation methods applied in the LTE system is applied.The coding method contents inform which coding method among a pluralityof coding methods applied in the LTE system is applied.

According to the second embodiment of the present invention, a pagingprocedure may be performed on the terminals in the RRC_Idle statewithout the physical paging indication channel (PICH). In the presentembodiment, when paging information is not generated, radio resourceapplicability (utilizable level) can be maximized by transmitting onlyscheduling information for the terminals without scheduling informationfor a paging message in the physical layer control channel information,and mapping and using available physical layer radio resources as DL-SCHfor data information transmission. Also, the radio resourceapplicability may be optimized through a method for flexibly allocatingthe radio resource of the physical layer based on the quantity of thegenerated paging information.

Part of the terminal scheduling ID may be reserved, allocated and usedby a group ID, and more than one group ID may be reserved and allocatedaccording to the capability of the terminal. The group ID may bebroadcasted through a system broadcasting channel. When the terminal isin a network, the group ID is managed according to each group andmanaged through modification/update based on a network environment.

FIG. 6 shows a physical layer control channel to which scheduling IDinformation is allocated and a radio resource to which paginginformation is variably allocated in accordance with the secondembodiment of the present invention.

According to a procedure in accordance with the embodiment describedabove, a radio resource as shown in FIG. 6 is formed and transmitted tothe terminal. The terminal receiving the radio resource searches acontrol channel 11 of the physical layer, recognizes the group IDreserved and allocated for transmission of paging information, which isgiven for the scheduler of the base station to identify the terminal orthe terminal group in a cell, receives and decodes paging informationtransmitted to the radio resource block 12 based on radio resource blockaddressing information. That is, the terminals may recognize whether thepaging message on the terminal group exists by searching a controlchannel and checking existence of the group ID reserved and allocatedfor transmission of the paging information in the scheduling informationof the control channel transmitted from the base station. Therefore,when there is no group ID for the paging message indicating own group inthe control channel, the terminals determine that the paging messagedoes not exist, and continuously performs a discontinuous receptionoperation. When the group ID exists, the terminals stop thediscontinuous reception operation and receive the paging message thatthe base station transmits on the radio resource addressed by the groupID.

In this case, a modulating and coding method of the block transmittingthe paging message broadcasts the paging message to the entire cellbased on the system information, or may transmit the paging messagethrough the scheduling information of the physical layer control channelas described above.

In the RRC_Connected state, when a state for low power consumption iscontrolled according to an activity factor occupying the radio resourcebetween the terminal and the base station in an MAC point of view, theterminal is operated by being divided into a duration of monitoringdownlink data and a duration of sleeping for performing low powerconsumption according to the discontinuous reception/discontinuoustransmission (DRX/TDX) cycle.

In the RRC_Connected state, when the terminal performs power savingoperation of monitoring a downlink signal on monitoring durationaccording to the discontinuous reception/discontinuous transmissioncycle, a paging procedure similar to the RRC_Idle state is required inthe monitoring duration of the terminal to start transmittinginformation on the downlink. The paging procedure is defined asindication to be differentiated from paging in the RRC_Idle state.Indication information is information notifying start of transmittingdownlink information from the base station to the terminal like thepaging information. Herein, in the RRC_Idle state, the RRC layer of thebase station is in charge of control, but in the RRC_Connected state,the RRC layer or the MAC layer is in charge of control relatively to thefunction of the scheduler.

When indication information for downlink information transmission in theRRC_Connected state is transmitted, the paging information transmittingmethod according to the embodiment described above may be used withoutany change. That is, the paging information transmitting method isadaptable by substituting indication information for downlinkinformation transmission for the paging information in the embodimentdescribed above.

To be specific, the scheduler of the base station transmits schedulinginformation, which is transmitted to the physical layer control channelaccording to the configured discontinuous reception/discontinuoustransmission cycle, including the terminal scheduling ID and radioresource allocation information for the terminal which should receiveindication information notifying downlink information transmission, orthe terminal group. Therefore, in the duration that the terminal in theRRC_Connected state performs monitoring according to the configureddiscontinuous reception/discontinuous transmission cycle, the terminalperforming low power consumption operation according to the activityfactor of the terminal searches the control channel of the physicallayer transmitted from the base station, recognizes a scheduling ID forthe terminal or the group ID reserved and allocated for indicationallowed to identify a terminal or a group in the cell by the schedulerof the base station, and receives and decodes the indication messagetransmitted on the radio resource block using the radio resourceallocation information. In this case, it is possible to broadcast themodulating and coding method of the block transmitting the indication tothe entire cell through the system information, or to transmit themodulating and coding method through the scheduling information of thephysical layer control channel.

It is also possible to include only the group ID reserved and allocatedfor the indication of downlink information in the physical layer controlchannel in order to reduce overhead due to control informationtransmission by reducing the size of the physical layer control channelinformation. In this case, the radio resource block 12 of the physicalchannel for the indication information can be fixed and operated in theinside of the corresponding TTI.

When the method of the second embodiment transmitting the indicationmessage through the control channel and the DL-SCH of the physical layerto notify downlink information transmission for the terminals in theRRC_Connected state is applied, the DL-SCH and the physical layercontrol channel can be used in the same method although the activityattribute of the terminal is different in the RRC_Connected state undercontrol of the scheduler and the MAC.

FIG. 7 shows an example that the radio resource of the physical layer isvariably allocated and operated corresponding to generation of thepaging information in accordance with an embodiment of the presentinvention.

As shown in FIG. 7 , only when paging information for the terminals inthe RRC_Idle state or downlink indication information for the terminalsin the RRC_Connected state is generated, the present invention occupiesthe radio resource of the physical layer and may efficiently operate thelimited radio resource.

As described above, the technology of the present invention can berealized as a program and stored in a computer-readable recordingmedium, such as CD-ROM, RAM, ROM, floppy disk, hard disk andmagneto-optical disk. Since the process can be easily implemented bythose skilled in the art of the present invention, further descriptionwill not be provided herein.

While the present invention has been described with respect to certainpreferred embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the scope of the invention as defined in the following claims.

1. (canceled)
 2. A wireless communication method, the method comprising:generating, at a base station, first information based on an identifier;generating, at the base station, paging information; transmitting, to auser equipment, the first information during a first transmission timeinterval (TTI), wherein the first TTI comprises a control channel and ashared channel, and the first information is transmitted in the controlchannel; and transmitting, to the user equipment, the paging informationduring the first TTI, wherein the paging information is transmitted inphysical layer radio resources of the shared channel identified by aportion of the first information, wherein the first information does notinclude any information indicating the user equipment.
 3. The method ofclaim 2, wherein: the paging information comprises another identifierwhich indicates that the paging information is intended for the userequipment; and the first information further indicates a coding schemefor the paging information.
 4. The method of claim 2, wherein the userequipment obtains the identifier based on the first informationaccording to a discontinuous reception (DRX) cycle and the userequipment is in Radio Resource Control (RRC) connected state.
 5. Themethod of claim 2, wherein the identifier indicates that paginginformation is to be transmitted.
 6. The method of claim 2, wherein: thephysical layer radio resources for the paging information are flexiblyallocated according to whether or not the paging information istransmitted in the shared channel.
 7. The method of claim 2, wherein:the identifier has a predetermined value which indicates that paginginformation is to be transmitted during the TTI.
 8. The method of claim2, wherein the paging information is obtained before the user equipmentdetermines the paging information is intended for the user equipment.